1. Field of the Invention
The present invention relates in general to the field of network analysis, and in particular to a method and an apparatus for connection or cabling exploration in a network during a computer boot process or during on-line operation.
2. Description of the Related Art
An input/output (I/O) expansion network in a known expandable computing system implements I/O fan-out with multiple I/O hubs and multiple I/O bridges. The I/O hubs are connected to a central processor complex (CPC) via connectors and a fixed board wiring. The I/O bridges located in I/O cages are attached with flexible cables to the I/O hubs located in CPC cages. Pairs of I/O bridges are connected with cables or via board wiring for fail-over redundancy. I/O channels are connected to the I/O bridges via connectors to a back-plane in the I/O cages.
In order to direct requests to the correct I/O channel, software/firmware needs to understand how to put together addresses so that they are routed to the correct I/O channel by the I/O expansion network.
The routing and the associated addresses on a topology that is fixed by connector slots and board wiring can be derived from the actual physical implementation of the wiring. The flexible cables introduce ambiguity in the addressing, since it is not known a priori which I/O bridges are connected to which I/O hubs. This is also true for redundancy connections between I/O bridges if they are implemented as flexible cables.
In said known expandable computing systems, the whole I/O expansion network is implemented with self-timed-interfaces (STIs). For the purpose of finding I/O hub to I/O bridge connections, STI cables contain an extra wire that does not contribute to the high-speed signaling and implies further cabling. Both I/O hub and I/O bridge contain interfaces to drive/receive current over this extra wire. In this environment, an exploration facility assigns unique identifiers for I/O hubs and I/O bridges based on their physical plug location if their presence was detected via side-band accesses. These unique identifiers are stored into a database together with a type to distinguish hubs from bridges. System control firmware then drives a current into the STI cable on an I/O hub and scans through all I/O bridges whether it detects an element receiving the current. The exploration facility then records a connection between the two database entries for the elements which have been found to be connected.
For subnet discovery in an InfiniBand architecture model, all network elements need to be operational at the transport layer, which means layer 4 of the OSI model, in order to receive, interpret queries through so-called subnet management packets by a subnet manager or the exploration facility and respond to these queries with subnet management packets (SMPs).
Internet protocol (IP) based networks requires that all the network elements need to be operational at least at the network layer, which means layer 3 of the OSI model.